1. Field of the Invention
The disclosures herein relate to a feeding device and an image forming apparatus.
2. Description of the Related Art
A feeding device for feeding sheets of paper on which an image is transferred is generally provided in image forming apparatuses such as an electronographic copier, a facsimile machine, a printer and a printer device. Such a feeding device may include a multi-feed preventing mechanism.
An example of the multi-feed preventing mechanism includes a mechanism configured to carry only a top one of layers of sheets S separately from the rest of the sheets S by utilizing the difference between the coefficient of friction of the layers of sheets S and the coefficient of friction of a transport member that comes into contact with the layers of sheets S.
FIGS. 9A, 9B and 9C are cross-sectional diagrams illustrating a configuration of a related art feeding device. The related art feeding device includes a multi-feed preventing mechanism formed of a pair of feed rollers 201 and 202 that come into contact with each other so as to move in cooperation with each other at a front part in a feeding direction indicated by an arrow F, and a carrying roller 203 located behind the pair of the feed rollers 201 and 202 and configured to be rotatable by intermittently coming into contact with a top one of the layers of sheets S loaded on a not-illustrated feed stand.
The feed roller 201 is located above the feed roller 202 and configured to be rotationally driven to feed the sheets S in a sheet feeding direction. The feed roller 202 is configured to be rotationally driven to transfer the sheets S in a returning direction opposite to the sheet feeding direction. The coefficient of friction between the pair of the feed rollers 201 and 202 and the layers of sheets S may include the following relationship.
Specifically, the coefficient of friction between the feed roller 202 and the remaining sheets S other than the top sheet is greater than the coefficient of friction between the layers of sheets S, and the coefficient of friction between the feed roller 201 and the top sheet is greater than the coefficient of friction between the feed roller 202 and the remaining sheets S. With this configuration, when the plural remaining sheets S other than the top sheet are carried together with the top sheet S, the top sheet S is carried by the feed roller 201 while the remaining sheets S1 (FIG. 9B) are returned in the returning direction opposite to the sheet feeding direction by rotational force of the feed roller 202.
The sheets returning toward the feeding device side from a transfer position, at which the top sheet S is sandwiched between the feed rollers 201 and 202, may be shifted in the sheet feeding direction from aligned rear ends of other remaining sheets loaded on the feed stand as illustrated in FIG. 9C.
In a case where the rear ends of the returning sheets are shifted in the sheet feeding direction and located behind the rear ends of the other remaining sheets, the returning sheets may shift (miss) the carrying position at which the carrying roller 203 carries the top sheet. As a result, the next sheet subsequent to the top sheet may not be carried.
Hence, in order to set rear end positions of the returning sheets S returning in the sheet feeding direction toward the feed stand side from the transfer position at which each of the sheets S is sandwiched between the feed rollers 201 and 202, a fence member 205 is arranged at a predetermined position in the feeding device as illustrated in FIGS. 9A and 9B. Accordingly, the rear end positions of the returning sheets are restricted to facilitate carrying of a next one of the sheets subsequent to the top sheet.
Recent image forming apparatuses are desired to be capable of forming images on sheets of various sizes or various types required by a user. Some of these image forming apparatuses may be configured to carry out bookbinding by themselves. In such an integrated bookbinding task, tab-attached sheets serving as index sheets may be utilized for assortment, delimiting, and header attachment.
FIG. 10 is a diagram illustrating arrangement of a tab-attached sheet, where (a) is a plan diagram of the tab-attached sheet and (b) is a schematic side diagram illustrating layers of the tab-attached sheets loaded on the feed stand.
In FIG. 10, when the feeding device transfers a tab-attached sheet TS, transfer failure may occur by simply pressing part of the tab-attached sheet TS. That is, as illustrated in FIG. 10, since it is necessary to restrict positions of rear ends of tabs T of the tab-attached sheets TS, the fence member 205 may be located in line with a position at which a dimension (indicated by “R” in FIG. 10) corresponding to a projected amount of the tab T is shifted rearward from the rear ends of the sheets TS.
However, in order for the next sheet to be carried, it may be necessary to locate a front end of the tab-attached sheet TS within a distance (indicated by Q in FIG. 10) from a position of a sheet end touching member 206 located corresponding to the front end side in the sheet feeding direction to a position at which the carrying roller 203 comes into contact with the tab-attached sheet TS.
Note that when a relationship Q>R is established, the next sheet may be carried. On the other hand, when a relationship Q<R is established, the front end of the sheet TS will not reach the carrying roller 203. As a result, the next sheet may not be carried.
However, some types of the tab-attached sheets include tabs formed at slightly different locations of the rear ends of the tab-attached sheets such that the tabs will not be located at the same positions of the tab-attached sheets. There are proposed numerous technologies that may employ sheets of a tab-attached sheet type having tabs slightly arranged at different locations of the rear ends of the sheets.
For example, Japanese Patent No. 3773724 (hereinafter also referred to as “Patent Document 1”) discloses a feeding device including an end fence to restrict positions of rear ends of the returned sheets S. The end fence includes a restricting face for arresting the rear ends of the sheets S in an entire width direction of the sheets S and is located on an upper surface of the top sheet of the layers of sheets S.
FIGS. 11A, 11B and 11C are diagrams illustrating an example of the related art feeding device. FIG. 11A is a perspective diagram of the end fence utilized in the related art feeding device, FIG. 11B is a perspective diagram of the related art feeding device and FIG. 11C is a cross-sectional diagram of the related art feeding device.
In the related art feeding device illustrated in FIGS. 11A, 11B and 11C, an end fence 215 is arranged on an upper surface of a top sheet of layers of tab-attached sheets TS loaded on the feed stand. As illustrated in FIGS. 11A and 11C, the end fence 215 includes a setting face 215A setting on the upper surface of the top sheet and a restricting piece extending from the setting face 215 and being folded at a right angle. The setting face 215A includes a “U-shape” in a horizontal view. The setting face 215A is configured to only touch a rear end and two ends in a width direction of the sheet S.
As illustrated in FIG. 11B, the restricting piece 215B includes a restricting face configured to touch the rear end of the sheet S in an entire width direction. Accordingly, a position of the rear end of the sheet S may be restricted in the entire width direction of the sheet S. The setting face 215A and the restricting piece 215B are symmetrically arranged based on a center of the sheet S in the width direction.
Due to diversified sizes and types of sheets of paper desired by users, a recent image forming apparatus may need to form images on sheets of various sizes and various types.
However, the end fence of the related art feeding device is compatible with only one type of a sheet size. Hence, plural end fences may need to be prepared when the user desired to use the tab-attached sheets of various types and various sizes.